I forgot my password how can I get into my iPhone 6s

See If you forgot your Apple ID password https://support.apple.com/en-us/HT201487

You also can use Having trouble signing in/iForgot https://iforgot.apple.com/password/verify/appleid 

And you will need to see If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

Before trying to answer your security questions is very important that you think about your questions, including your birth date, and their answers carefully and try to recall all details you can. If you don't answer them correctly enough, then you easily can lose control of your account.

Passcode?

Read here -> If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Apple ID password?

Read here -> https://iforgot.apple.com

https://support.apple.com/en-us/HT201487

You can find a solution at the link above.

I wish you good health.

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